Seventy-eight patients have now been admitted to the primary protocol for the treatment of non-Hodgkins's lymphoma, and the goals of this protocol, namely, to define different prognostic groups within this broad category of patients have largely been achieved. Utilizing a CHOP - high dose methotrexate regimen, the results in lymphoblastic lymphoma without marrow involvement and patients with entirely resected intraabdominal undifferentiated lymphoma or localized disease have been excellent (currently 100% and 92% disease-free survival). Among the remaining patients the most important prognostic feature is bone marrow involvement. With the exception of this category, even patients with extensive undifferentiated lymphomas have a disease-free survival rate of about 50%. These findings will be incorporated into protocols now under development in which treatment will be tailored to prognostic groups. Overall, the results of the present protocol show a 15% improvement in terms of disease-free survival over the two previous protocols used in the Pediatric Branch, when the previous results are combined (justified on the basis of a previous multi-institutional study which showed no difference in outcome between these protocols). A detailed analysis of staging studies in undifferentiated lymphoma in children has been completed. This indicates the value of gallium scanning which gave no false negative results in the abdomen. Gallium is inferior to ultrasound or CAT scan in detecting hepatic lesions, and to a chest x-ray in detecting pleural effusions. A negative scan of the abdomen, however, is sufficient to exclude intraabdominal disease, obviating the need for further imaging studies except for helping to determine resectability and in determining whether hydronephrosis is present. No skeletal lesions were detected on bone scan which were not also seen on gallium scan.